Stair climbing is recognized as a particularly effective type of aerobic exercise, and as a result, exercise machines facilitating this type of exercise are popular for both home and health club use.
There have been a variety of approaches taken in designing stair climbing apparatus, including the simulation of an actual staircase as illustrated in U.S. Pat. Nos. 3,497,215, 3,747,924, 4,687,195, 5,183,448, 5,263,909 5,299,993 and 5,336,143. Another approach has been to simulate the action of stair climbing by using a pair of reciprocating pedals.
As exemplified by U.S. Pat. No. 5,135,447, reciprocating pedal machines include a pair of pedals which are adapted for vertical reciprocating motion to provide a user who is standing on the pedals with a simulated climbing exercise. The vertical reciprocating motion is typically translated into a rotary motion by a suitable system of belts, gears and clutches, for example. The rotary motion (which can be imparted to a shaft, flywheel or the like) is opposed by a variable source of resistance force, typically an alternator, eddy current brake or the like. The load device is responsive to a control signal for selectively varying the level of resistance.
Other previous attempts at simulating stair climbing exercisers, such as Potts, U.S. Pat. No. Re. 34,959, feature independently oscillating pedals wherein the speed may be controlled and monitored by the operator, or may be preselected, controlled and monitored by computer control programs. Some such apparatuses produce an unnatural heel to toe flexure that reduces exercise efficiency. As will be appreciated, in the present invention, the foot pedal assembly remains parallel to a support surface throughout its entire range of motion, as the foot pedal assembly travels from its upper position to its lower position, thereby producing a more natural heel to toe flexure which increases exercise efficiency, making it easier and more enjoyable to exercise.
Additionally, the Potts disclosure simulates stair climbing through the utilization of a four-bar linkage pedal system and a frame plate. One disadvantage of this mechanism is that the angle in which the drive belts are connected to the pivot arms supporting the pedals varies as the pedals move up and down. This results in variations in tension in the belt, torque loads and ultimately variations on the resistance applied to the pedals. Also, such four-bar linkage pedal systems with frame plates tend to be noisy, have numerous pinch points, and substantially increase manufacturing and repair expense. Moreover, due to the large number of pivot points in this type of linkage, the linkages frequently become loose and require frequent maintenance. As a result, it is desirable to decrease the manufacturing expense, improve the smoothness of pedal motion, reduce maintenance costs and decrease noise of stair climbing apparatuses.
Another previous stair climbing exercise apparatus Is disclosed in Doll et al, U.S. Pat. No. 5,741,205. In this apparatus, cables or belts are substituted for the four bar linkage of Potts which eliminates some of the mechanical problems of this arrangement. However, the varying angle of connection of the belt to the pedal support member remains.
In general, the objective of these systems is to simulate stair climbing. Stair climbing is characterized by its uniform, repetitive nature. Ideally, stair climbing apparatuses would provide a more dynamic climbing simulation to increase user interest. A need therefore exists for an improved stair climbing apparatus.